U.S. Pat. No. 6,219,140 discloses a device for compensating for spectral fluctuations in a light source. The device has photodiodes, in particular, which detect the red, green and blue spectral regions of a light source. The image signals detected by a photodetector are corrected in accordance with the spectral intensity distribution determined by the photodiodes in order to compensate for variations in the image signals which are caused by spectral fluctuations in the illumination.
Taking this as a departure point, it is desirable to provide a device which permits the compensation of variations in an image signal which are caused by fluctuations in the illumination.